The present invention relates to the art of diagnostic imaging. It finds particular application in conjunction with single-photon emission computed tomography (SPECT) with single or multi-headed cameras and will be described with particular reference thereto. It is to be appreciated, however, that the invention will also find application in other non-invasive investigation techniques such as single photon planar imaging, whole body nuclear scans, positron emission tomography (PET) and other diagnostic modes.
Heretofore, single photon emission computed tomography has been used to study a radionuclide distribution in subjects. Typically, one or more radiopharmaceuticals are injected into a subject. The radiopharmaceuticals are commonly injected into the subject's blood stream for imaging the circulatory system or for imaging specific organs which absorb the injected radiopharmaceuticals. Gamma or scintillation camera heads are placed closely adjacent to a surface of the subject to monitor and record emitted radiation. In single photon-emission computed tomography, the head is rotated or indexed around the subject to monitor the emitted radiation from a plurality of directions. The monitored radiation data from the multiplicity of directions is reconstructed into a three dimensional image representation of the radiopharmaceutical distribution within the subject.
Each camera head typically includes a flat scintillation crystal which converts incident radiation to flashes of light. Internal electronics convert each flash of light into an indication of the location and energy of the received incident radiation event. Collimators are commonly mounted to the face of each camera head such that the scintillation crystal only receives radiation travelling along preselected rays. Generally, the collimators are a series of lead vanes arranged in a grid that limit the rays to parallel rays, diverging rays in a fan or cone pattern or the like. The height of the vanes and their spacing control the degree which received radiation may vary from the selected rays. Different collimators are provided for different types of medical procedures.
A variety of devices have been placed between the collimator and the subject in an effort to improve image resolution. However, placing devices between the collimator and the subject increases the distance between the subject and the camera head which decreases the image resolution.
Transmission radiation sources have been placed opposite the patient from a detector head. In one or three detector head systems, space is available to mount the radiation source. In a two head system, mounting the source opposite one head places it in front of the other. Its own collimator and shielding further increases the distance between the crystal and the subject in two detector head systems.
The present invention contemplates a new and improved collimator apparatus which overcomes the above-referenced problems and others.